Dispersing insecticides or other pesticidal compounds as vapors



June 19; 1951 Y E. H. WHEELWRIGHT ETAL 2,557,815'

DISPERSING INsEcTIcIDEs 0R OTHER PESTICIDAL COMPOUNDS AS VAPDRS Filed NOV. 16, 1949 MRQM /47T0fP/VEY Patented `une 19, 1951 UNITED STATES PATENT OFFICE DISPERSING INSECTICIDES OR OTHER PESTICIDAL COMPOUNDS AS VAPORS Application November 16, 1949, Serial No. 127,769 In Great Britain November 15, 1948 9 Claims.

This invention relates to dispersing insecticides or other pesticidal compounds and is more particularly concerned with the method and means of dispersing insecticidal compounds by smoke generation, in which the pesticidal compound is admixed with a self-combustible composition which is capable of burning under confined conditions, and which on burning vaporises the pesticidal compound.

It is the usual practice to enclose a charge of the self-combustible composition with the pesticidal compound admixed in it in a container such as an aluminium or card-board tube which is open at one end, so that when the composition is ignited it burns slowly vaporising the pesticidal compound which issues from the open end of the container as a vapour or smoke in admikture with combustion gases produced by burning of the self-combustible composition.

It is Well-known that the vapours generated by some compositions iname unless special precautions are taken, that is, the vapours catch lire immediately on issuing from the container. The inamng is thought to be due to the fact that the presence of a small quantity of air on the surface of the burning composition is su'- cient to cause the vapours to ignite. For example, it is well-known that smoke generating compositions containing insecticide azobenzene (benzeneazo-benzene), which is used for killing Red Spider, are particularly subject to the disadvantage of inaming.

It has therefore been proposed to provide a container in which the charge of the self-burning composition and pesticidal compound is separated from the ultimate outlet from the container by one or more mechanical baies, formed for example from perforated metal sheets, so that the vapours and combustion gases cannot flow directly from the composition to atmosphere. Such an arrangement is disadvantageous' in that with small containers the mechanical baiting means occupies a large proportion of the space within the container, thereby reducing the quantity of the composition that can be charged into a container. so that for a given size of container a relatively small space can be treated with the pesticidal compound.

This invention has for an object to provide improved means for dispersing pesticidal compounds in the form of vapours in which the necessity for such mechanical baffling to prevent inammation of the vapours generated can be avoided.

It has been found that certain burning compositions instead of leaving a powdery ash when burnt form a porous bonded mass through which the generated vapour or smoke can pass and which can itself act as a bale, and this invention employs this fact to form a baie between a composition, the vapours of which will inflame, and the outlet from a container.

Accordingly this invention provides generator means for dispersing a vaporisable insecticide comprising a container with an outlet at one end and a charge of self-combustible material in the container which charge is formed in two or more layers whereof the uppermost layer, that is the layer nearest the outlet, is a composition which forms on combustion a porous bonded mass permitting the passage of vapours through it and which does not generate an imiaming vapour, and whereof the other or one at least of the other layers is a pesticidal smoke generating composition the vapours ofwhich will inname.

In the use of the smoke generator according to this invention the uppermost layer burns rst leaving the porous bonded mass bridging the outlet from the container so that when the lower layer or layers of the charge burn the vapours generated have to pass through the porous mass to the outlet; in this way on issuing into the at mosphere the vapours will be separated from their generating charge and cannot be caused to inname due to burning of the charge. Moreover the porous bonded mass has a strength su'cient to withstand the gas pressures Within the container without breaking up and being ejected from the container; this avoids a further disadvantage of known smoke generators, not having mechanical bafes, that hot fragments of the residue formed on combustion are often ejected from the container.

The uppermost layer need form only a small proportion of the total charge in the container so that even though the uppermost layer does not itself produce a pesticidal vapour, a large proportion of the container can be occupied by a pesticidal smoke generating composition. However according to a feature of this invention the uppermost layer may contain a vaporisable pesticidal composition and Where this feature is adopted it will be seen that the whole of the container can be occupied by a pesticidal smoke generating composition.

In one preferred form of this invention the uppermost layer of the charge consists of a composition comprising heXamine, potassium chlorate or other suitabie highly oxygenated inorganic compound, diatomaceous silica or kaolin which is preferably in a finely divided state (such as the material known as colloidal kaolin) or nely divided native magnesium silicate (such as talc) or another chemically inert substance of like physical properties, and a material which is vaporised by the combustion of the hexamine with oxygen supplied by the highly oxygenated inorganic compound. The vaporisable material may be an insecticide or other pesticidal compound, for example D. D. T. or may be a substantially non-toxic compound such as hexachloroetliane.

It has been found that, on combustion, a composition containing these substances produces a hard bonded mass having Iine pores running through it, which mass can act as a baiile to prevent inammation of the vapours generated by the combustion of the other pesticidal compound dispersing compositions.

The vaporisable compound such as D. D. T. or

hexachloroethane may form the major portion of the composition forming the upper layer and it is preferred that the ratio of the quantity or vaporisable compound to the quantity of hexamine and highly oxygenated inorganic compound combined shall lie within the limits 1:1 and 3.021.

The quantity of highly oxygenated inorganic compound such as potassium chlorate present should be insucient to cause complete combustion of the hexamine and is preferably present in a quantity having a ratio of 1.1:1 and 5.0:1 to the quantity of hexamine employed.

The chemically inert substance, such as diatomaceous silica or colloidal kaolin, appears to exert a controlling influence on the size of the pores running through the hard bonded mass and I;

the quantity of this substance added to the composition may be varied. It is preferred, however, that the quantity of the chemically inert substance added shall lie within the range of 4% to 18% of the total weight of the composition from which the uppermost layer is formed.

One composition having a high eiciency as a bathe-forming composition comprises 57 parts by weight of D. D. T. or hexachloroethane, 20 parts by weight of potassium chlorate, 8 parts by weight of hexamine, l2 parts by weight of diatomaceous silica, and 3 parts of thiourea.

Another composition which is suitable for this purpose comprises 6l parts by Weight of D. D. T. or hexachloroethane, 21 parts by weight of potassium chlorate, 9 parts by weight of hexamine and from 4 to 9 parts by weight of diatomaceous silica or colloidal kaiolin.

Another composition which has been found to be suitable for forming the porous crust comprises as its essential constituents a vaporisable material, a highly-cxygenated inorganic compound, thiourea and urea. The urea acts as a moderant to prevent the thicurea from burning at an excessive rate and also acts as a stabilizer for the chlorate in the presence of impure D. D. T. One suitable composition of these constituents comprises- 61% D. D. T. 23% potassium chlorate 11% thiourea and 5% urea The thickness of the uppermost layer may be varied considerably but a minimum thickness is required to prevent inflammation of vapours generated from a composition below it, which minimum thickness is dependent on the size of the aperture in the container.

It will be clear that the invention is not limited to using a thickness of the uppermost layer just sufficient to form a baiile for the vapours generated by the lower layer or layers of the charge. For instance it is sometimes desirable to disperse azobenzene (benzeneazo-benzene) for killing Red Spider and D. D. T. for killing other insects and this may be achieved by partially lling the container with a self-combustible composition 'containing the azobenzene, the vapours of which readily inflame and cover this charge with a layer of a D. D. T. composition such as those above set forth, the depth of the layers being selected according to the desired ratio of the azobenzene and D. D. T.

According to a feature of this invention therefore means for dispersing vaporisable pesticidal compounds as above set forth may be employed for dispersing two or more pesticidal compounds, by incorporating a pesticidal compound in each of a number of the layers of the charge.

There will now be described a test carried out on a smoke generator prepared according to this invention, reference being made in the description to the accompanying drawings, in which:

Fig. 1 is a sectional view taken through the longitudinal axis of the generator; and

Fig. 2 is a view of the upper end of the generator.

Referring now to the drawings, the generator comprises an aluminum tube Ill 90 mm. long and 37 mm. in diameter, which tube is closed at one end and has at the other end a closure disc II perforated with a plurality of holes I2 each 6 mm. in diameter, there being a spacing of 8 mm. between the centres of each pair of adjacent holes. the tube I0 is partially filled with 82 grams of a powdered composition, indicated at I3, comprising:

Per cent by weight Azobenzene 47 Potassium chlorate 20 Sucrose 2l and Colloidal kaolin 12 is then spread evenly over the top of the azobenzene composition I3 to give a layer 1 cm. thick.

The surface of the layer of construction I4 is dusted with an igniter composition, indicated at I5, comprising;

61 by weight D. D. T. 23% by weight potassium chlorate 11% by weight thiourea.

5% by weight urea and covered by a paper disc I6. The apertured closure disc II is then placed in position.

On ignition of the charge the smoke generated is first a white smoke and then an orange smoke, showing that the azobenzene is being vaporised,

but no inammation of the azobenzene vapour occurs.

When the container has cooled down the wall of the aluminium container is cut away and the upper layer is removed, it is found that the layer I4 is a hard cake having pores running through it. The residue oi the azobenzene charge, however, readily crumples to powder form.

Similar results are obtained in tests in which the D. D. T. was replaced by hexachloroethane, and in which the diatomaceous silica was replaced by colloidal kaolin.

We claim:

1. Pesticidal smoke generating means having a container provided with an outlet at one end thereof, and a charge Within the container, said charge comprising a self-combustible composition in adm ixture with a vaporisable pesticidal substance, said charge being formed in at least two layers having dicrent compositions, the layer adjacent the outlet having a composition to form on combustion a. porous bonded mass permitting the passage of vapours therethrough and generating a non-inflaming vapour, a layer remote from the outlet being arranged to generate on combustion an iniiaming pesticidal vapour containing gas.

2. Pesticidal smoke generating means having a container provided with an outlet at one end thereof, and a charge within the container, said charge comprising a self-combustible composition in admixture with a vaporisable pesticidal substance, said charge being formed in a plurality of layers of differing compositions and containing diiering vaporisable pesticidal substances, the end layer adjacent the outlet from the container having a composition to form on burning of the layer a porous bonded mass permitting the passage of vapours therethrough, at least another layer having a composition to generate on combustion an iniiaming pesticidal vapour containing gas.

3. Pesticidal smoke generating means having a container provided with an outlet at one end thereof, and a charge within the container, said charge comprising a self-combustible composition in admixture with a' vaporisable pesticidal substance, said charge being formed in at least two layers having diierent compositions, the layer adjacent the outlet having a composition to form on combustion a porous bonded mass permitting the passage of vapours therethrough and generating a non-iniiaming vapour, a layer remote from the outlet being arranged to generate on combustion an inflaming pesticidal vapour containing gas, the layer adjacent the outlet comprising in admixture hexamine, a highly oxygenated inorganic compound in a quantity insufficient to cause complete combustion of the hexamine, a vaporisable substance, and a chemically inert substance which on burning of the composition assists in the formation of a porous bonded residue.

4. Pesticdal smoke generating means according to claim 3, wherein the ratio of the quantity of the vaporisable substance to the quantity of hexamine and highly oxygenated inorganic com- 6 pound combined lies within the limits 1.3:1 and 3.0:l, and the ratio of the quantity of the highly oxygenated inorganic compound to the quantity of hexamine present lies within the limits of from 1.1:1 to 5.011.

5. Pesticidal smoke generating means according to claim 3, wherein the ratio of the quantity of the vaporisable substance to the quantity of hexamine and highly oxygenated inorganic compound combined lies within the limits 1.3:1 and 3.0: l, and the ratio of the quantity of the highly oxygenated inorganic compound to the quantity of hexamine present lies within the limits of from 1.1:1 to 50:1, and wherein the chemically inert substance is present in a proportion of from 4% to 18% by weight of the total weight of the composition forming the uppermost layer.

6. Pesticidal smoke generating means according to claim 1, wherein the layer adjacent the outlet comprises in admixture 57 parts by weight of D. D. T., 20 parts by weight of potassium chlorate, 8 parts by weight of hexamine, 12 parts by weight of diatomaceous silica and 3 parts by weight of thiourea.

7. Pesticidal smoke generating means according to claim 1, wherein the layer adjacent the outlet is formed by a composition comprising 6l parts by weight of D. D. T., 21 parts by weight of potassium chlorate, 9 parts by weight of hexamine, and from 4 to 9 parts by weight of colloidal kaolin.

8. Pesticidal smoke generating means according to claim 1, wherein the layer adjacent the outlet is formed by a composition comprising 61 parts by weight of hexachloroethane, 21 parts by weight of potassium chlorate, 9 parts by weight of hexamine, and from 4 to 9 parts by Weight of diatomaceous silica.

9. Pesticidal smoke generating means according to claim l, wherein the layer adjacent the outlet is formed from a composition comprising in admixture D. D. T., potassium chlorate, thiourea and urea, the latter acting as a moderant for the speed of burning' of the thiourea and as a stabilizer in storage for the chlorate, with the said ingredients being present in proportion by Weight of 61:23:1115, in the order named.

EDVJARD HANLEY WHEELWRIGHT. JOHN MERRITT DINSDALE. PHYLLIS MAY HOLL/IES.

PAMELA RUTH MARTIN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,207,766 Katzenberger Dec. l2, 1916 2,154,221 Taylor Apr. 11, 1939 2,385,636 McLain Sept. 25, 1945 2,440,082 Flanders Apr. 20, 1948 2,488,776 Jones Nov. 22, 1949 FOREIGN PATENTS Number Country Date 397,238 Great Britain Aug. 24, 1933 

1. PESTICIDAL SMOKE GENERATING MEANS HAVING CONTAINER PROVIDED WITH AN OUTLET AT ONE END THEREOF, AND A CHARGE WITHIN THE CONTAINER, SAID CHARGE COMPRISING A SELF-COMBUSTIBLE COMPOSITION IN ADMIXTURE WITH A VAPORISABLE PESTICIDAL SUBSTANCE, SAID CHARGE BEING FORMED IN AT LEAST TWO LAYERS HAVING DIFFERENT COMPOSITIONS TO LAYER ADJACENT THE OUTLET HAVING A COMPOSITION TO FORM ON COMBUSTION A POROUS BONDED MASS PERMITTING THE PASSAGE OF VAPOURS THERETHROUGH AND GENERATING A NON-INFLAMING VAPOUR, A LAYER REMOTE FROM THE OUTLET BEING ARRANGED TO GENERATE ON COMBUSTION AN INFLAMING PESTICIDAL VAPOUR CONTAINING GAS. 